Method of making a preformed curved epidural catheter

ABSTRACT

A length of polytetrafluoroethylene tubing is passed over a rigid curved mandrel and then heated to a temperature above approximately 620*F to cause the tubing to become clear. The tubing is rapidly cooled to cause the tubing to set in a curved shape. The tubing is then removed from the mandrel and permitted to stabilize. A portion of the tubing adjacent an end is then stretched and the end of the stretched portion trimmed to form a curved catheter.

United States Patent Vaillancourt et a1.

[ 1 March 6, 1973 METHOD OF MAKING A PREFORMED CURVED EPIDURAL CATHETERInventors: Vincent L. Vaillancourt, Livingston. Thomas H. Bohner,Berkely Heights, both of NJ.

Assignee: C. R. Bard lnc Murray Hill, NJ.

Filed: Dec. 9, 1970 Appl. No.: 96,593

Related US. Application Data Continuation of Ser. No. 822,677, May 7,1969, abandoned.

US. Cl ..264/162, 128/349 R, 264/285, 264/292, 264/296 Int. Cl. ..B28b11/10, B290 17/02 Field of Search ..264/127, 162, 285', 292, 296;128/349 R References Cited UNITED STATES PATENTS 1/1966 Jeckel ..128/349R X 2,941,911 6/1960 Kumnick et all ..264/127 X 2,998,985 9/1961 Burnset a1. ..264/295 2,642,625 6/1953 Peck 264/l27 X 3,085,290 4/1963 Chu..264/127 FOREIGN PATENTS O R APPLICATIONS 6,511,556 3/1966 Netherlands..264/127 Primary ExaminerPhilip E. Anderson Att0rneyW. Saxton Seward[57] ABSTRACT A length of polytetrafluoroethylene tubing is passed overa rigid curved mandrel and then heated to a temperature aboveapproximately 620F't0 cause the tubing to become clear. The tubing israpidly cooled to cause the tubing to set in a curved shape. The tubingis then removed from the mandrel and permitted to stabilize. A portionof the tubing adjacent an end is then stretched and the end of thestretched portion trimmed to form a curved catheter.

5 Claims, 6 Drawing Figures PATENTEUHAR 61973 FIG.I

INVENTORS, V. L. VAILLANCOURT BY THOMAS H. BOHNER mom W1 Mow ATTORNEYSMETHOD OF MAKING A PREFORMED CURVEI) EPIDURAL CATHETER This applicationis continuation of application Ser. No. 822,677, filed May 7, 1969 andnow abandoned.

In order to bend a plastic (e.g. Teflon) epidural catheter to a desiredset curvature, a plastic tube is passed loosely over a rigid mandrel ofthe generally desired shape, the portion to be curved is heated, theheated tubing is stretched to draw down its diameter and effect at leastpartial orientation as well as attenuation, the tubing is cut to thedesired length and the mandrel is removed. The curved catheter may beplaced on a straight mandrel to be externally tipped by grinding to forma tapered end.

When a plastic catheter is inserted, with the aid of a needle, in theepidural space it is desirable to have the tip portion of the catheterangled with respect to the axis of the needle in order that it may liein the space, after withdrawal of the needle, with its open endextending in the proper direction and in a position such that danger ofobstruction to flow is minimized. An angle greater than 30 is found tobe satisfactory.

Many crystalline plastic materials can be given a semi-permanent set (ofvarying durability) by merely holding the article in or beyond itsdesired deformed position for an extended period of time and effortshave been made to lock in such deformations by heating the article, butit has been found that, with or without heating, the inherent memory ofmost plastics causes a more or less gradual return to the original formunless the plastic is quenched (quickly cooled). This is intolerable inarticles which may be used at times from a few days to several monthsafter manufacture, the actual form of each article being a function ofan unknown shelf time, and possible other factors. If the crystallineplastic is quenched, it warps and distorts rendering it unusable formany purposes.

For use in connection with epidural operations a preferred cathetermaterial is Teflon" TFE and the present invention will be described withparticular reference to this material, but without restriction except asexpressly noted. A catheter needle assembly in which the-catheterdisclosed herein may desirably be used as described in I-Ienkinapplication Ser. No. 655,513, filed July 24, 1967, now U.S. Pat. No.3,506,007, and relating to an improved epidural catheter needle for theintroduction and placement of a catheter and the administration ofepidural anesthesia or drainage.

A practical embodiment of the present invention is illustrated in theaccompanying drawing to which the description refers.

FIG. 1 represents an elevation of a mandrel;

FIG. 2 represents an axial sectional view of the mandrel with plastictube thereon;

FIG. 3 represents an axial sectional view as in FIG. 2 with the tube endheated and stretched;

FIG. 4 represents an axial sectional view of the completed catheter;

FIG. 5 represents an elevation of the catheter on a needle, ready forinsertion; and I FIG. 6 represents an elevation of the catheter in theposition assumed after insertion and partial withdrawal of the needle.

The pre-formed catheter is made by providing a mandrel 1 of a suitablematerial such as stainless steel,

of uniform diameter and bent smoothly near one end through an angle ofabout A piece of Teflon TFE tubing 2, having an ID. slightly larger thanthe diameter of the mandrel, is threaded on the mandrel and extends ashort distance beyond the bent end thereof as indicated at 3, theclearance between the mandrel and tube being designated 4.

The tube and mandrel are then heated above the transition temperature ofTeflon TFE, which is approximately 620 F., causing the tubing to becomeclear, and a pulling force is applied to the end 3 of the tube. As thetubing is drawn (FIG. 3) it is attenuated and its diameter is reduced,in the zone 5, to that of the mandrel, at which point the assembly isquenched in water, setting a bend in the tube which, upon removal fromthe mandrel, stabilizes at about 60.

The tube 2 is removed from the mandrel I, placed on a straight mandrel(not shown), trimmed to remove excess material 6 at the tip, andexternally finished by grinding to form the smooth taper or bevel 7(FIG. 4).

For epidural administrations a catheter made of Teflon TFE is preferredin order to decrease frictional drag through the body tissue andligaments. Other polymeric materials exhibiting similar self-lubricatingcharacteristics include the organopolysiloxanes and linear polyethylene.

In use, a needle 8 having a slightly rounded beveled end 9 (the bevelbeing at an angle of no less than 30 or greater than 90 from the needleaxis) is inserted through the catheter to a position where it projectsslightly beyond the tapered end of the catheter, as shown in FIG. 5. Thecatheter and needle are held accurately in this relationship as they areintroduced, for instance, through the interspinous ligaments into theepidural space, the relatively blunt end of the needle minimizing dangerof puncturing the dura. When the catheter has been thus introduced intosaid space, and its proper orientation determined by a suitable indexingmark (not shown), the needle can be withdrawn, first to the positionshown in FIG. 6 where the catheter has returned to its prc-setcurvature, and then completely to leave the catheter lumen open andunimpeded for administration or drainage, as required.

The bend in the catheter end ensures that flow through it, in eitherdirection, cannot be blocked by contact with the dura.

What we claim is:

l. The method of making a preformed curved plastic catheter whichincludes the steps of providing a rigid curved mandrel having acurvature greater than that desired in the final product, passing alength of polytetrafluoroethylene tubing over said .mandrel whereby thetubing is deformed to the shape of the mandrel, heating the assembledmandrel and tubing to a temperature above approximately 620 F., causingthe tubingto become clear, rapidly cooling the heated assembly to setthe tubing in a curved shape, separating the tubing from the mandrel andpermitting the tubing to stabilize at the desired curvature.

2. The method according to claim 1 wherein the heating is followed bydrawing and stretching a portion of the tubing adjacent an end of saidtubing, whereby the diameter ofthe stretched portion is reduced.

3. The method according to claim 2 which includes trimming off an endportion of the tubing adjacent the stretched portion.

4. The method according to claim 3 which includes beveling the endportion of the tubing adjacent the stretched portion.

5. The method according to claim 4 wherein the beveling is effected byplacing the curved tube on a 5 straight mandrel and grinding the portionto be beveled.

1. The method of making a preformed curved plastic catheter whichincludes the steps of providing a rigid curved mandrel having acurvature greater than that desired in the final product, passing alength of polytetrafluoroethylene tubing over said mandrel whereby thetubing is deformed to the shape of the mandrel, heating the assembledmandrel and tubing to a temperature above approximately 620* F., causingthe tubing to become clear, rapidly cooling the heated assembly to setthe tubing in a curved shape, separating the tubing from the mandrel andpermitting the tubing to stabilize at the desired curvature.
 1. Themethod of making a preformed curved plastic catheter which includes thesteps of providing a rigid curved mandrel having a curvature greaterthan that desired in the final product, passing a length ofpolytetrafluoroethylene tubing over said mandrel whereby the tubing isdeformed to the shape of the mandrel, heating the assembled mandrel andtubing to a temperature above approximately 620* F., causing the tubingto become clear, rapidly cooling the heated assembly to set the tubingin a curved shape, separating the tubing from the mandrel and permittingthe tubing to stabilize at the desired curvature.
 2. The methodaccording to claim 1 wherein the heating is followed by drawing andstretching a portion of the tubing adjacent an end of said tubing,whereby the diameter of the stretched portion is reduced.
 3. The methodaccording to claim 2 which includes trimming off an end portion of thetubing adjacent the stretched portion.
 4. The method according to claim3 which includes beveliNg the end portion of the tubing adjacent thestretched portion.